Interactions between bivalves and zooplankton: competition or intraguild predation? Implications for biomanipulation in subtropical shallow lakes

2017 ◽  
Vol 68 (6) ◽  
pp. 1036 ◽  
Author(s):  
Soledad Marroni ◽  
Néstor Mazzeo ◽  
Juan Pablo Pacheco ◽  
Juan Clemente ◽  
Carlos Iglesias

Zooplankton and bivalves are the main consumers of phytoplankton in shallow lakes; however, knowledge regarding trophic interactions between them is scarce. Competition for resources appears to be an obvious direct interaction, but the scheme may be more complex. Bivalves can consume all or only part of the zooplankton, constituting an intraguild predation module. In the present study we investigated the interaction between bivalves and zooplankton and its effects on phytoplankton grazing and community structure using an experimental approach in an aquarium. Two bivalve species were considered, namely Diplodon parallelopipedon (native) and Corbicula fluminea (non-native), in addition to a natural zooplankton community dominated by small-sized zooplankton. The findings indicate that phytoplankton consumption by the zooplankton is substantially less than that by the bivalves. Under the experimental conditions, the bivalves actively consumed small-sized zooplankton (rotifers and nauplii), but no consumption of medium-sized individuals (cladocerans and copepods) was observed. The differential consumption may have implications on the size and structure of zooplankton, favouring an average larger-sized community. Thus, phytoplankton may be negatively affected both directly by consumption and indirectly because of the resulting structure of the zooplankton community. The main results of the study are also discussed from the perspective of biomanipulation techniques in tropical and subtropical regions.

2019 ◽  
Vol 47 (12) ◽  
pp. 1353-1363 ◽  
Author(s):  
Yolande Piris ◽  
Nathalie Guibert

Purpose The purpose of this paper is to investigate consumers’ variety perception for online grocery assortments and, more generally, to better understand consumers’ attitude toward digital assortments. In particular, this research examines the influence of the organization of products that results from assortment structure and display. Design/methodology/approach Starting from the observation that previous work on traditional assortments is not sufficient to understand consumers’ perceptions and attitudes, the paper adopts a hypothetico-deductive approach and develops four hypotheses. These hypotheses are tested using an experimental approach. Findings This research enables us to see that both attitude and variety perception are affected by the way products are organized on a website. Furthermore, contrary to what the literature on traditional assortments allows one to assume, the assortment corresponding to a more positive attitude is not perceived as being the more varied. As a result, our findings reconsider the link between variety perception and consumer assortment evaluation for digital assortments. Research limitations/implications The work is based on data collected for only one product category. It would be interesting to explore other categories also, to determine if the structure of the assortment and variety perception have stable effects. Practical implications The results inform retailers that they must carefully design the display of their digital assortments. If a retailer wants to enhance variety perception, the authors recommend using an assortment organized by brand, or presenting all the products together. If, instead, the goal is to encourage a positive attitude, the retailer should opt for assortments sorted by attribute or that present all products together. Originality/value This research adopts a new orientation on assortment perception and evaluation, considering the specificities involved in digitizing assortments. In addition, this research studies a real product category and puts respondents in experimental conditions close to reality.


2013 ◽  
Vol 46 (6) ◽  
pp. 1842-1853 ◽  
Author(s):  
Cristian Mocuta ◽  
Marie-Ingrid Richard ◽  
Julie Fouet ◽  
Stefan Stanescu ◽  
Antoine Barbier ◽  
...  

Structural anisotropy, for example texture, may govern important physical properties of thin film, such as electrical, magnetic and/or mechanical ones. Texture (orientation information) is typically observed and quantified by the measurement of so-called pole figures. An optimized experimental approach implemented at the DiffAbs beamline (Synchrotron SOLEIL) is presented here. Using an X-ray pixel area detector and synchrotron radiation sources, a complete pole figure (with resolutions adapted for metallic textured thin films, typically of the order of a few degrees) can be measured in time intervals as short as one minute. The necessary corrections enabling complete pole figure retrieval from the experimental data using this optimized approach are provided and discussed. A gain in measuring time by up to two orders of magnitude is found with respect to the use of a point detector (classical approach) under the same experimental conditions. Data measured using these two approaches are shown, compared and discussed.


1996 ◽  
Vol 135 (4) ◽  
pp. 1059-1069 ◽  
Author(s):  
H Volkmer ◽  
R Leuschner ◽  
U Zacharias ◽  
F G Rathjen

Neurofascin and NrCAM are two axon-associated transmembrane glycoproteins belonging to the L1 subgroup of the Ig superfamily. In this study, we have analyzed the interaction of both proteins using neurite outgrowth and binding assays. A neurofascin-Fc chimera was found to stimulate the outgrowth of tectal cells when immobilized on an inert surface but not as a soluble form using polylysine as substrate. Antibody blocking experiments demonstrate that neurite extension on immobilized neurofascin is mediated by NrCAM on the axonal surface. Under the reverse experimental conditions where NrCAM induces neurite extension, F11, and not neurofascin, serves as axonal receptor. Binding studies using transfected COS7 cells and immunoprecipitations reveal a direct interaction between neurofascin and NrCAM. This binding activity was mapped to the Ig domains within neurofascin. The neurofascin-NrCAM binding can be modulated by alternative splicing of specific stretches within neurofascin. These studies indicate that heterophilic interactions between Ig-like proteins implicated in axonal extension underlie a regulation by the neuron.


2021 ◽  
Author(s):  
Yu Liu ◽  
Job Dekker

The ring-like cohesin complex mediates sister chromatid cohesion by encircling pairs of sister chromatids. Cohesin also extrudes loops along chromatids. Whether the two activities involve similar mechanisms of DNA engagement is not known. We implemented an experimental approach based on isolated nuclei carrying engineered cleavable RAD21 proteins to precisely control cohesin ring integrity so that its role in chromatin looping could be studied under defined experimental conditions. This approach allowed us to identify cohesin complexes with distinct biochemical, and possibly structural properties, that mediate different sets of chromatin loops. When RAD21 is cleaved and the cohesin ring is opened, cohesin complexes at CTCF sites are released from DNA and loops at these elements are lost. In contrast, cohesin-dependent loops within chromatin domains and that are not anchored at CTCF sites are more resistant to RAD21 cleavage. The results show that the cohesin complex mediates loops in different ways depending on genomic context and suggests that it undergoes structural changes as it dynamically extrudes and encounters CTCF sites.


1984 ◽  
Vol 1 (19) ◽  
pp. 116 ◽  
Author(s):  
Isao Irie ◽  
Kazuo Nadaoka

Mechanism of scour in front of breakwaters by standing waves in two and three dimensions has been studied theoretically and experimentally to clarify the experimental conditions by which the prototype behavior could be best reproduced in laboratory. The phenomenal reproduction of scour in laboratory is satisfactory if some conditions on the characteristics of waves and bed materials are fulfilled. This enables experimental approach to find out the optimum protection methods against scour in front of breakwaters.


2018 ◽  
Vol 1148 ◽  
pp. 176-186 ◽  
Author(s):  
D. Maneaih ◽  
K. Prahlada Rao ◽  
K. Brahma Raju

Two sheets of aluminium 6061-T6 alloy of size 400×150×3 (mm) is butt welded by the friction stir welding by varying the process parameter such as rotational speed, tilt angle and feed. The ranges of process parameters are rotational speed 560, 900 and 1400 RPM, tilt angle 0, 0.5 and 1 and feed 20, 63 and 100 mm/min. The hexagonal shape of probe is taken to carry out the friction stir welding. The Taguchi L9 experimental approach is used to draw the 9 experimental conditions. The temperature at the weld bead as well as on the probe during the welding is measured by the help of a LASER gun. The hardness at the weld bead and parent metal is measured after the welding. Taguchi L9 approach is used to optimize the process parameters to identify the individual as well as simultaneous effects of the process parameters on the responses temperature and hardness of the weld joint. The optimum conditions for the better fitment of the process parameter and responses are identified through this experimentation.


2003 ◽  
Vol 10 (3) ◽  
pp. 147-157 ◽  
Author(s):  
Theodore G. Jones ◽  
Jacob Grun ◽  
L. Dale Bibee ◽  
Charles Manka ◽  
Alexandra Landsberg ◽  
...  

Underwater shocks and bubbles were generated using a high energy pulsed laser system. The advantages of this experimental approach are: (1) precisely controlled and measured experimental conditions; (2) improved diagnostics, including extensive imaging capabilities; (3) unique experiments, including a simultaneously detonated line charge; and (4) the ability to provide validation quality data for hydrodynamic simulation codes. Bubble sensitivity to variation of several experimental parameters was examined. Numerical simulations were performed corresponding to the experimental shots, showing that empirical bubble theory, experimental bubble data, and simulations were all in good agreement.


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